MmDebstrap

# MmDebstrap task

The `mmdebstrap` task fully implements the SystemBootstrap interface.

On top of the keys defined in that interface, it also supports the following additional keys in `task_data`:

- `bootstrap_options`

  - `use_signed_by` (defaults to True): if set to False, then we do not pass the keyrings to APT via the `Signed-By` sources.list option, instead we rely on the `--keyring` command line parameter.

The task computes dynamic metadata as:

- subject: suite name in the first `bootstrap_repositories`

- parameter_summary: subject (architecture-variant)

- runtime_context: `$architecture:$variant:$extra_packages` of `bootstrap_options`

- configuration_context: `architecture` of `bootstrap_options`

The keys from `bootstrap_options` are mapped to command line options:

- `variant` maps to `--variant` (and it supports more values than debootstrap, see its manual page)

- `extra_packages` maps to `--include`

The keys from `bootstrap_repositories` are used to build a sources.list file that is then fed to `mmdebstrap` as input.